Fossil Lutrinae are very rare in the Plio-Pleistocene fossil record. We report here a right mandible of an otter from the Early Pleistocene of the Upper Valdarno Basin (Italy) kept in the collections of the Natural History Museum of London. The specimen, recovered in the XIX century, remained undescribed until today. Morphologic and morphometric characters of the mandible allow us to refer it to Lutra simplicidens Thenius, 1965, a fossil otter recorded in Europe in the late Early to Middle Pleistocene, thus representing the oldest report of this species. This finding adds a new interesting taxon to the late Villafranchian faunal assemblage of the Upper Valdarno and reinforces the hypothesis of an African origin of L. simplicidens, because of its affinities with L. fatimazohrae Geraads, 1997 from Morocco.